package com.ctim.common.tool.encrypt;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;


public class Base64 {

	/**
	 * how we separate lines, e.g. \n, \r\n, \r etc.
	 */
	private String lineSeparator = System.getProperty("line.separator");

	/**
	 * max chars per line, excluding lineSeparator.  A multiple of 4.
	 */
	private int lineLength = 72;

	/* constructor */
	public Base64() {
	}

	/**
	 * Encode an arbitrary array of bytes as Base64 printable ASCII.
	 * It will be broken into lines of 72 chars each.  The last line is not
	 * terminated with a line separator.
	 * The output will always have an even multiple of data characters,
	 * exclusive of \n.  It is padded out with =.
	 */
	public String encode(byte[] b) {
		// Each group or partial group of 3 bytes becomes four chars
		// covered quotient
		int outputLength = ((b.length + 2) / 3) * 4;

		// account for trailing newlines, on all but the very last line
		if (lineLength != 0) {
			int lines = (outputLength + lineLength - 1) / lineLength - 1;
			if (lines > 0) {

				outputLength += lines * lineSeparator.length();
			}
		}

		// must be local for recursion to work.
		StringBuffer sb = new StringBuffer(outputLength);

		// must be local for recursion to work.
		int linePos = 0;

		// first deal with even multiples of 3 bytes.
		int len = (b.length / 3) * 3;
		int leftover = b.length - len;
		for (int i = 0; i < len; i += 3) {
			// Start a new line if next 4 chars won't fit on the current line
			// We can't encapsulete the following code since the variable need to
			// be local to this incarnation of encode.
			linePos += 4;
			if (linePos > lineLength) {
				if (lineLength != 0) {
					sb.append(lineSeparator);
				}
				linePos = 4;
			}

			// get next three bytes in unsigned form lined up,
			// in big-endian order
			int combined = b[i + 0] & 0xff;
			combined <<= 8;
			combined |= b[i + 1] & 0xff;
			combined <<= 8;
			combined |= b[i + 2] & 0xff;

			// break those 24 bits into a 4 groups of 6 bits,
			// working LSB to MSB.
			int c3 = combined & 0x3f;
			combined >>>= 6;
			int c2 = combined & 0x3f;
			combined >>>= 6;
			int c1 = combined & 0x3f;
			combined >>>= 6;
			int c0 = combined & 0x3f;

			// Translate into the equivalent alpha character
			// emitting them in big-endian order.
			sb.append(valueToChar[c0]);
			sb.append(valueToChar[c1]);
			sb.append(valueToChar[c2]);
			sb.append(valueToChar[c3]);
		}

		// deal with leftover bytes
		switch (leftover) {
			case 0:
			default:

				// nothing to do
				break;

			case 1:

				// One leftover byte generates xx==
				// Start a new line if next 4 chars won't fit on the current line
				linePos += 4;
				if (linePos > lineLength) {

					if (lineLength != 0) {
						sb.append(lineSeparator);
					}
					linePos = 4;
				}
				// Handle this recursively with a faked complete triple.
				// Throw away last two chars and replace with ==
				sb.append(encode(new byte[]{b[len], 0, 0}
				).substring(0, 2));
				sb.append("==");
				break;

			case 2:

				// Two leftover bytes generates xxx=
				// Start a new line if next 4 chars won't fit on the current line
				linePos += 4;
				if (linePos > lineLength) {
					if (lineLength != 0) {
						sb.append(lineSeparator);
					}
					linePos = 4;
				}
				// Handle this recursively with a faked complete triple.
				// Throw away last char and replace with =
				sb.append(encode(new byte[]{b[len], b[len + 1], 0}
				).substring(0, 3));
				sb.append("=");
				break;

		} // end switch;

		if (outputLength != sb.length()) {
			System.out.println("oops: minor program flaw: output length mis-estimated");
			System.out.println("estimate:" + outputLength);
			System.out.println("actual:" + sb.length());
		}
		return sb.toString();
	} // end encode

	/**
	 * decode a well-formed complete Base64 string back into an array of bytes.
	 * It must have an even multiple of 4 data characters (not counting \n),
	 * padded out with = as needed.
	 */
	public byte[] decode(String s) {

		// estimate worst case size of output array, no embedded newlines.
		byte[] b = new byte[(s.length() / 4) * 3];

		// tracks where we are in a cycle of 4 input chars.
		int cycle = 0;

		// where we combine 4 groups of 6 bits and take apart as 3 groups of 8.
		int combined = 0;

		// how many bytes we have prepared.
		int j = 0;
		// will be an even multiple of 4 chars, plus some embedded \n
		int len = s.length();
		int dummies = 0;
		for (int i = 0; i < len; i++) {

			int c = s.charAt(i);
			int value = (c <= 255) ? charToValue[c] : IGNORE;
			// there are two magic values PAD (=) and IGNORE.
			switch (value) {
				case IGNORE:

					// e.g. \n, just ignore it.
					break;

				case PAD:
					value = 0;
					dummies++;
					// fallthrough
				default:

					/* regular value character */
					switch (cycle) {
						case 0:
							combined = value;
							cycle = 1;
							break;

						case 1:
							combined <<= 6;
							combined |= value;
							cycle = 2;
							break;

						case 2:
							combined <<= 6;
							combined |= value;
							cycle = 3;
							break;

						case 3:
							combined <<= 6;
							combined |= value;
							// we have just completed a cycle of 4 chars.
							// the four 6-bit values are in combined in big-endian order
							// peel them off 8 bits at a time working lsb to msb
							// to get our original 3 8-bit bytes back

							b[j + 2] = (byte) combined;
							combined >>>= 8;
							b[j + 1] = (byte) combined;
							combined >>>= 8;
							b[j] = (byte) combined;
							j += 3;
							cycle = 0;
							break;
					}
					break;
			}
		} // end for
		if (cycle != 0) {
			throw new ArrayIndexOutOfBoundsException(
					"Input to decode not an even multiple of 4 characters; pad with =.");
		}
		j -= dummies;
		if (b.length != j) {
			byte[] b2 = new byte[j];
			System.arraycopy(b, 0, b2, 0, j);
			b = b2;
		}
		return b;

	} // end decode

	/**
	 * determines how long the lines are that are generated by encode.
	 * Ignored by decode.
	 *
	 * @param length 0 means no newlines inserted. Must be a multiple of 4.
	 */
	public void setLineLength(int length) {
		this.lineLength = (length / 4) * 4;
	}

	/**
	 * How lines are separated.
	 * Ignored by decode.
	 *
	 * @param lineSeparator may be "" but not null.
	 *                      Usually contains only a combination of chars \n and \r.
	 *                      Could be any chars not in set A-Z a-z 0-9 + /.
	 */
	public void setLineSeparator(String lineSeparator) {
		this.lineSeparator = lineSeparator;
	}

	/**
	 * letter of the alphabet used to encode binary values 0..63
	 */
	static final char[] valueToChar = new char[64];

	/**
	 * binary value encoded by a given letter of the alphabet 0..63
	 */
	static final int[] charToValue = new int[256];

	/**
	 * Marker value for chars we just ignore, e.g. \n \r high ascii
	 */
	static final int IGNORE = -1;

	/**
	 * Marker for = trailing pad
	 */
	static final int PAD = -2;

	static
	/* initialise valueToChar and charToValue tables */ {
		// build translate valueToChar table only once.
		// 0..25 -> 'A'..'Z'
		for (int i = 0; i <= 25; i++) {
			valueToChar[i] = (char) ('A' + i);
			// 26..51 -> 'a'..'z'
		}
		for (int i = 0; i <= 25; i++) {
			valueToChar[i + 26] = (char) ('a' + i);
			// 52..61 -> '0'..'9'
		}
		for (int i = 0; i <= 9; i++) {
			valueToChar[i + 52] = (char) ('0' + i);
		}
		valueToChar[62] = '+';
		valueToChar[63] = '/';

		// build translate charToValue table only once.
		for (int i = 0; i < 256; i++) {
			charToValue[i] = IGNORE; // default is to ignore
		}

		for (int i = 0; i < 64; i++) {
			charToValue[valueToChar[i]] = i;
		}

		charToValue['='] = PAD;
	}

	/**
	 * used to disable test driver
	 */
	private static final boolean debug = false;

	/**
	 * debug display array
	 */
	public static void show(byte[] b) {
		for (int i = 0; i < b.length; i++) {
			System.out.print(Integer.toHexString(b[i] & 0xff) + " ");
		}
		System.out.println();
	}

	/**
	 * debug display array
	 */
	public static void display(byte[] b) {
		for (int i = 0; i < b.length; i++) {
			System.out.print((char) b[i]);
		}
		System.out.println();
	}

	public String testDataInputStream(String filepath) throws IOException {
		File file = new File(filepath);
		DataInputStream din = new DataInputStream(new FileInputStream(file));
		StringBuilder hexData = new StringBuilder();
		byte temp = 0;
		for (int i = 0; i < file.length(); i++) {
			temp = din.readByte();
			// 以十六进制的无符号整数形式返回一个字符串表示形式。
			String str = Integer.toHexString(temp);
			if (str.length() == 8) {//去掉补位的f
				str = str.substring(6);
			}
			if (str.length() == 1) {
				str = "0" + str;
			}
			hexData.append(str.toUpperCase());
		}
		return hexData.toString();
	}
}
